Long Term Evolution (LTE) is a radio technology designed to increase the capacity and speed of mobile telephone networks and provides for an end-to-end Internet Protocol (IP) service delivery of media. Currently, LTE comprises a set of enhancements to the Universal Mobile Telecommunications System (UMTS), which is described in a suite of Technical Specifications (TS) developed within and publicized by 3rd Generation Partnership Project (3GPP), with the most recent version of the 3GPP TSs being published in September 2010.
LTE, in part, provides for a flat IP-based network architecture designed to ensure support for, and mobility between, some legacy or non-3GPP systems such as, for instance, GPRS (general packet radio service) and WiMAX (Worldwide Interoperability for Microwave Access). Some of the main advantages with LTE are high throughput, low latency, plug and play, FDD (frequency-division duplexing) and TDD (time-division duplexing) in the same platform, improved end user experience, simple architecture resulting in low operating costs, and interoperability with older standard wireless technologies such as GSM (Global Systems for Mobile Communications), cdmaOne™, W-CDMA (UMTS), and CDMA2000®.
Many major carriers in the United States (US) and several worldwide carriers have started to convert their networks to LTE. In addition, public safety agencies in the US (including US Intelligence Services) have endorsed LTE as the preferred technology for the new 700 MHz public safety radio band.
Due to the mission critical nature of public safety, it is important that user equipment (UE) operated by public safety personnel maintain service continuity while moving throughout the LTE system. More particularly, when a UE undergoes a handover from one cell to another cell, as the UE moves in the LTE system, it is essential that the UE move to a cell that supports the UE's current channel (for continuity of service) or at a minimum supports at least one channel of interest to the UE. However, this is not always possible in current LTE systems.
Current LTE systems typically contain numerous cells covering multiple geographical areas, with many of these cells supporting different groups of channels. Current mechanisms of selecting a cell for UE handover utilize signal strength measurements, wherein, for example, the cell with the strongest signal could be selected as a target for handover. However, this is not sufficient to guarantee continuity of service since the strongest signal does not necessarily come from a cell that carries or is capable of carrying a channel of interest for a given UE; and, in the case of Multimedia Broadcast Multicast Service (MBMS) channels, the selected cell may not even support the channel on which the UE is active or any channels of interest to the UE, for that matter.
Thus, there exists a need for a method and system for selecting a target cell for handover of UE in an LTE system.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of various embodiments. In addition, the description and drawings do not necessarily require the order illustrated. It will be further appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. Apparatus and method components have been represented, where appropriate, by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the various embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art, having the benefit of the description herein. Thus, it will be appreciated that for simplicity and clarity of illustration, common and well-understood elements that are useful or necessary in a commercially feasible embodiment may not be depicted in order to facilitate a less obstructed view of these various embodiments.